The subject matter described herein relates generally to semiconductor processing, and to electroless plating of metal layers on aluminum metal gate transistors.
Access to and operation of semiconductor devices, such as, transistors, resistors, capacitors, and the like is typically provided by one or more contacts to the devices. As the density of circuits of semiconductor devices increases with each subsequent generation, device pitches shrink by an average of 20-50%, significantly increasing the risk of shorting the interconnect to source or drain (collectively referred to herein as the contact), to the Interconnect to the gate. The decrease in pitch necessitates a fix to the shorting phenomena between the interconnect to the source/drain to the interconnect to the gate (this will be referred to herein as contact to gate shorting).
Contact to gate shorting during the semiconductor device manufacturing will create a short circuit in the semiconductor device resulting in the loss of the entire die (yield loss). For example, a contact opening may be intended to permit access to a source/drain region of a semiconductor device. If a misalignment occurs during the semiconductor device manufacturing process, when the misaligned contact opening is filled with metallic material, the contact to the source/drain will form a short circuit to the contact to the Gate resulting in the loss of the entire chip.
Semiconductor device manufacturers have developed self-aligned contact (SAC) technology to alleviate these problems. Conventional (SAC) manufacturing processes involve forming a electrolessly deposited sacrificial metal or metal alloy cap layer on a copper gate, which is formed on a semiconductor substrate.
Some semiconductor devices use aluminum as a gate interconnect. Aluminum commonly forms a thin layer of aluminum oxide, which is a highly stable passivated surface. The layer of aluminum oxide inhibits the subsequent selective deposition of the sacrificial metals or metal alloys on the aluminum layer by electroless deposition. Therefore, it is not possible to implement a SAC flow on devices with Al gate interconnects. This shortcoming is addressed by this invention.
For simplicity and clarity of illustration, the drawing Figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing Figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the Figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different Figures denote the same elements.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used.